# CVE-2026-109167: TDuck survey form through 6.0 Authorization Bypass via User-Controlled Theme ID in POST /user/form/theme/save

> Authenticated attackers can overwrite other users' form themes by manipulating theme IDs, leading to unauthorized data modification.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Oct 2026
- **Updated:** 14 Oct 2026
- **Also known as:** GHSA-w8cw-4mm2-mrw7

## What is CVE-2026-109167?

CVE-2026-109167 is a medium-severity missing authorization vulnerability in TDuckCloud tduck-survey-form, published on 12 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

TDuck survey form through 6.0 contains an insecure direct object reference vulnerability in the saveFormTheme handler that allows authenticated users to overwrite other users' form themes. Attackers whose form has no theme can submit another form's sequential theme id with their own formKey, replacing its colours and image URLs and removing the victim's theme.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-109167?


## How do I fix CVE-2026-109167?

No fix has been published for CVE-2026-109167 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-109167 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109167 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109167 and fix it if it is affected.

What it is: CVE-2026-109167 is a medium-severity missing authorization vulnerability in TDuckCloud tduck-survey-form, published on 12 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109167 exists.

Affected product: TDuckCloud tduck-survey-form. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-109167/ (Markdown: https://insights.sbomify.com/CVE-2026-109167/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109167
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109167
- OSV: https://osv.dev/vulnerability/CVE-2026-109167

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109167/
Summaries are generated and may contain mistakes; the official description above is the record.